Abstract

A combination of visual line-transect survey, photo-identification (photo-ID), and automated acoustic monitoring methods is being used to gather important baseline information on the occurrence, distribution, and density of marine mammals near Naval Station Norfolk (NSN) and adjacent areas. The study area was chosen to cover areas where United States (U.S.) Navy activity is substantial, including Chesapeake Bay waters near Naval Station Norfolk, Joint Expeditionary Base (JEB) Little Creek (LC), and JEB Fort Story, as well as a Mine Exercise (MINEX) Area (W-50) in the Atlantic off the coast of Virginia Beach, Virginia. Twenty-five line-transect surveys were completed in two zones (INSHORE and MINEX) between August 2012 and November 2013, with 2,810 kilometers (km) and 8,942 minutes completed on-effort. The majority of sightings were bottlenose dolphins (Tursiops truncatus), although humpback whales (Megaptera novaeangliae) and short-beaked common dolphins (Delphinus delphis) were also sighted in the study area on occasion. In addition, loggerhead sea turtles (Caretta caretta) and leatherback sea turtles (Dermochelys coriacea) were sighted during the study period. Conventional line-transect analysis of bottlenose dolphin sightings showed both spatial and seasonal variation in density and abundance, with greatest abundance in the INSHORE zone during summer months. INSHORE densities were calculated as 3.05 individuals per square kilometer (km2) (N=948) in fall, 0.40 individuals per km2 (N=123) in winter, 1.09 individuals per km2 (N=337) in spring, and 3.52 individuals per km2 (N=1,094) in summer. MINEX densities were calculated as 0.11 individuals per km2 (N=105) in fall, 0.00 individuals per km2 (N=0) in winter, 0.10 individuals per km2 (N=90) in spring, and 0.16 individuals per km2 (N=148) in summer. A photo-ID catalog was created using photos taken during both dedicated photo-ID and line-transect surveys through July 2013; it contains 308 identified individuals to date. Thirty-three individuals were re-sighted; however, most sightings were less than three months and 15 km apart. Additional survey effort will be required before any clear movement patterns can be determined. C-POD acoustic data loggers (www.chelonia.co.uk) were deployed at four sites throughout the study area to cover areas of high U.S. Navy activity. Harbor porpoises (Phocoena phocoena) were detected in low numbers near NSN and JEB-LC during winter and spring deployments, and bottlenose dolphins were detected in each deployment location during all deployments from August 2012 to September 2013. Deployments, however, did not provide consistent coverage due to loss of gear. Further study is required to improve accuracy in seasonal density estimates and allow further stratification of those estimates, and to better describe the movement patterns and site fidelity of the bottlenose dolphins in these waters. Visual surveys and additional C-POD deployments are currently planned through August 2014.

Purpose

The HDR Marine Species Monitoring (MSM) Team was tasked to initiate a monitoring project in coastal waters around NSN, JEB-LC, JEB-FS, and the Virginia Beach waterfront, including the VACAPES MINEX W-50 training area. The main objective is to provide quantitative data and information on the seasonal occurrence, distribution, and density of marine mammals. Effort was dedicated to working with local researchers and employing proven marine mammal monitoring and research techniques to accomplish the following:

Attributes

Overview

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downlodable online. Other attributes may be obtained upon provider's permission unless otherwise noted below.

This section explains attributes included in the original dataset.
OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only.
Should you need other attributes described here, you are encouraged to contact the data provider.

The amount of glare (0-100%) on the left (port) side of the platform. Refers to glare from 0 to 90 degrees, or viewshed for which observer is reponsible (percent).

glareright

The amount of glare (0-100%) on the right (starboard) side of the platform. Refers to glare from 270-360 degrees, or viewshed for which observer is reponsible (percent).

groupid

Identifier for a particular group within a sighting

headinganimal

Heading of the animal at the time of the initial sighting (in degrees magnetic)

headingplatmagnetic

Heading of the observation platform relative to magnetic North in degrees

headingplattrue

Heading of the observation platform relative to true North in degrees

horizsun

Horizontal glare calculation on NOAA large vessel surveys (1 o

latitude

The calculated latitude of the animal at the initial time of the sighting in decimal degrees

latplatform

The latitude of the platform in decimal degrees

latvessel

The latitude of the vessel(s) (NOT the survey platform) sighted during a survey in decimal degrees

legid

Letter or number for survey leg/transect

legnotes

Notes as entered for that particular leg of the survey

legnumber

A unique identifier for the leg associated with the survey

linearity

A metric describing animal travel, calculated by dividing the distance between the first and last recorded sighting waypoints by the sum total of all distances between waypoints. Values range between 0 and 1, with a number closer to 1 representing a straight line and close to 0 representing no constant direction of the animal.”

longitude

The calculated longitude of the animal at the initial time of the sighting in decimal degrees

longplatform

The Longitude of the platform in decimal degrees

longvessel

The longitude of the vessel(s) (NOT the survey platform) sighted during a survey in decimal degrees

mitigation

Was mitigation implemented? (Y/N)

mitigationtype

Type of mitigation implemented

navydirectedleg

Marker identifying whether the platform was directed by the Navy to go to a certain location, fly at a certain altitude, or leave the immediate area (Y/N)

observer

The name of the observer who first sighted the animal

observeraft

Name of the observer in the aft position

observercenter

Name of the observer in the center position or belly window of the aircraft

observerforward

Name of the observer in the forward position

observerleft

Name of the observer on the left (port) side of the platform

observerrearleft

Name of the observer in the rear left seat of the aircraft

observerrearright

Name of the observer in the rear right seat of the aircraft

observerright

Name of the observer on the right (starboard) side of the platform

ocean

The ocean where the survey took place (Pacific, Atlantic, Indian, etc.)

opticstype

Indicates the type of optic used to fix a particular sighting (e.g., bigeyes, handheld binos, theodolite, naked eye). Useful when a platform uses several methods to sight animals

ordnance

Was live ordnance in use at the time of the sighting? (Y/N)

percentcloudcover

Cloud cover as represented by a percentage (percent)

percentcloudcoverleft

Cloud cover on the left (port) side of the platform as represented by a percentage (percent)

percentcloudcoverright

Cloud cover on the right (starboard) side of the platform as represented by a percentage (percent)

photoframes

The photo frames used for the sighting; or total frames taken

photogapher

Name of the photographer

photos

Were photos taken as part of the sighting? (Y/N)

pic

Pilot in command

platformded

Indicates if the survey was a dedicated marine mammal survey, or if data was gathered opportunistically from a platform on a different mission (Y/N)

The type of reaction at the initial time of the sighting relative to the observation platform

reactioninitcount

The general count of animals that initially reacted to the observation platform. May be a number or text (i.e., "whole group")

reactionlater

Identifies whether a reaction occurred as a response to the survey platform after the initial sighting of the group/individual

reactionlatercount

The number of animals that reacted to the observation platform after the sighting occurred

recorder

Name of the person recording data

recorderfocal

Name of the person recording focal follow data

reorientationrate

A magnitude of course changes along the trackline, calculated by summing all course changes (degrees) along the trackline divided by duration (minutes) of the trackline (Smultea and Wursig, 1995; course changes/minute).

resolution

Bathymetric resolution in arc degrees at sighting position in decimal degrees